Pedal Away the Pounds

I am a 46-year-old, 5'2", 128 lb woman in good health. I would like to lose 5 pounds. I just got a stationary bike that I plan to ride every day for exercise. How many calories will I burn riding my stationary bike and how many calories should I be eating to maintain my goal weight?

Ah, the calories question! Yours is a popular one, as most women are mystified by how many calories they burn and how many they should consume. The simple equation is 1 pound = 3,500 calories. But anyone who's tried to lose weight knows it's not that simple.

How many calories you burn each day is determined by a number of factors, including your resting metabolic rate, or "metabolism," (how many calories you burn just living and breathing), your daily activity level (sit at a desk vs. carry packages all day), and how much you exercise.

In your case, if you were to ride your bike every day for 45 minutes at a moderate pace, meaning you're breathing slightly hard, you would burn about 350 calories a day. (You can use the Prevention.com calorie burner as a guide.) At that rate, you would lose a little more than a half pound a week.

Now the trickier part of the equation: What should your daily intake be to maintain your goal weight? Dietitians use the following formula to estimate daily calorie requirements:

In your case: Your RMR at 123 lbs would be 1,230. If like many Americans, you work a desk job, you can add about 25 percent for daily activity (@300 calories), making it 1,530 per day. Then add 350 for your exercise, for a grand total of 1,880 per day.

That equation is a great place to start, but there is plenty of room for error. The best way to determine your RMR is to get it tested. A relatively new device called the BodyGem measures the rate you burn oxygen to calculate your metabolism. It's as easy as breathing into a mask for a few minutes. They're available at health clubs and gyms around the country. Check HealtheTech to find a facility near you. Screening typically costs around $65.

On a side note: Riding your stationary bike daily is an admirable goal, but your body--and your brain--might respond even better to a little diversity. Try adding some other activity, like walking/jogging, dancing, swimming, and strength training, to work your muscles in new ways and burn even more calories.